unswitch.c

#include <stdbool.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char **argv) {
    int A[1000000];
    int B[1000000];

    int i = 1000000;
    int j = 1000000;
    int s;

    bool same = strcmp(argv[1], "0");

    while(i > 0 && (same || j > 0)) {
        i--;
        if(same)
            j = i;
        else
            j--;

        s += A[i] * B[j];
    }